SHINDO3

Osaka High Court

Personal data~6,000accounts

EXPOSEDEmail address / Nickname / display nameMisconfiguration · Closed (final report)

Open in the live monitor ▶
Disclosed
Sep 4, 2026
Detected
Aug 27, 2026 12:20 JST
Detection to disclosure
8 days
Leak
Exposed, access unknown
Type
Misconfiguration
Status
Closed (final report)
Security spend
Measures, no amount
Compensation
Not announced

What leaked

IdentityUser name
ContactEmail address

How many

  • Accounts registered by mistake ~6,000 accounts
  • Users outside the court ~3,500 accounts
  • Court staff users ~2,500 accounts

Who is affected

  • Users outside the court
  • Court staff users

Cause

When the civil division created a Teams team for a specific case, about 6,000 accounts other than the intended members were registered by mistake

Timeline

  1. Exposure began
  2. Found after an outside inquiry; the team was deleted
  3. Exposure ended
  4. Reported by the press on September 4 (piyolog)

Response

  • Data deleted

Deleted the wrongly created team and posted an apology and contact points

What you should do

  1. Don't open links in emails from this company. The apology email itself may be fake
  2. You can be affected without ever using this service (parcel recipients etc.). Check any notice you receive
  3. Expect targeted phishing posing as HR or interview contacts
  4. Check the company's notice to see if you're affected

Lessons for companies

  1. Two-person review and pre-release tests for sharing and cache changes; monitor cloud config (CSPM)
  2. Use DLP: recipient checks, send delay, automatic attachment protection
  3. Report to the PPC: preliminary in 3–5 days, final in 30 (60 if malicious)
  4. Run red teaming and AI-assisted hardening, and publish how much you invest

Sources